: ( 648nf)
Black attaches at the upper edge.

:
White stops Black from getting an eye at the left edge.

:
Black gives atari at the top.

He might consider giving atari at , instead, but he will be unable to win the subsequent ko fight. He will lose the entire upper left corner, and so the game by a large margin.

:
White connects, turning the upper left corner into a seki.

White will win the game by over 10 points